Electric motor powered pumps are widely used to transport water from rivers, irrigation canals, wells and other sources for agricultural, drinking water and other applications. In urban areas and regions where electric utility power is readily available, this power is used to power the motor/pump in a controlled and dependable manner. In remote areas where electrical power may not be as readily available, internal combustion engine powered systems are used as a more expensive alternative.
With increasing costs of fossil fuels and environmental issues, solar power has become more popular in recent years. This has been aided by significant cost reductions due to the development of low cost technologies and subsidies provided by governments worldwide. As a result, solar powered pumping systems are often more cost-effective than engine powered systems in many remote and rural areas.
An important issue with solar energy powered pumping systems is the variable nature of the power source. In conventionally powered pumps (i.e. utility or engine powered systems), this is not a factor since electric power is available on demand as long as the electric current limits and engine sizing have been done properly. In these systems, the pumping rate is readily controlled by throttling the flow (i.e. via valves, etc.), or by motor (or engine) speed control which can be accomplished by varying the input voltage (for dc motors) or the frequency (for ac motors). In contrast, practical implementation of solar powered systems is much more difficult due to changing outdoor conditions. Not only does this result in variable power availability, but the voltage output of PV systems also varies with the incident solar intensity. Thus, a solar powered pumping system must necessarily be more complex to ensure that the varying available power is properly used.